Owner’s manual
Should I use 87 or 91 gas for lawn mower?
For the Craftsman lawn mower model 24738911, use regular unleaded 87 octane (87 AKI) as your everyday fuel. Higher octane (like 91) does not add power or improve reliability in this mower; it is simply unnecessary when the engine is designed for 87. See the fuel requirements in the 24738911 owner's manual.
Use fuel that matches the mower’s requirements and avoids common fuel-related starting problems.
- Use clean, fresh, unleaded gasoline
- Use 87 octane minimum (87 AKI)
- Gasoline with up to 10% ethanol (E10) is acceptable
- Gasoline with up to 15% MTBE is acceptable
- Do not use E85
- Do not mix oil into the gasoline
In normal conditions, it does not. Octane is mainly about resistance to knock in higher-compression engines. Most walk-behind mower engines are built to run correctly on 87, so 91 typically provides no benefit.
| Option | What you get | What we recommend |
|---|---|---|
| 87 octane (regular) | Meets the mower’s minimum requirement | Best choice for routine mowing |
| 91 octane (premium) | Higher knock resistance | Not needed for this model |
Fuel quality and storage habits matter more than octane.
- Buy only what you will use in 30 days
- Store gas in an approved container, tightly sealed
- Keep the fuel tank area clean so dirt and water do not enter
- If storing the mower over 30 days, run it dry or use a fuel stabilizer as described in the 24738911 owner's manual
Using the correct fuel (fresh, unleaded, 87 octane minimum) helps prevent carburetor varnish, hard starting, and rough running. Choosing 91 instead of 87 usually just increases cost without improving performance.
Last updated: January 2026
What is the average lifespan of a gas lawn mower?
A gas walk-behind lawn mower like the Craftsman 24738911 typically lasts 10 years with normal residential use and consistent maintenance; many run 8 to 15 years overall. Following the oil, air filter, spark plug, and cleaning schedule in the 24738911 owner's manual is the biggest factor in reaching the high end of that range.
- Average residential lifespan: about 10 years
- Common overall range: 8 to 15 years
- Heavy use or poor maintenance: often under 8 years
- Well-maintained, light use: often 15+ years
| Usage pattern | Typical hours/year | Typical lifespan |
|---|---|---|
| Light residential | 10 to 20 | 12 to 15 years |
| Average residential | 20 to 25 | About 10 years |
| Heavy residential | 40+ | 6 to 10 years |
The manual’s maintenance schedule calls out routine checks and service intervals that protect the engine and deck.
- Check engine oil level each use
- Change engine oil after the first 5 hours, then at regular intervals
- Clean or replace the air cleaner on schedule (more often in dusty conditions)
- Replace the spark plug on schedule
- Clean the underside of the mower deck to reduce corrosion and airflow restriction
- Before storage, run the engine out of fuel or treat fresh fuel with stabilizer
Most “mower lifespan” failures are really fuel system and engine wear problems caused by old gas, dirty oil, or restricted airflow. Staying on top of oil changes, air filtration, and off-season storage prevents hard starting, power loss, and premature engine damage.
- Repeated no-start or hard-start issues even after tune-up basics
- Noticeable loss of power under normal grass load
- Excessive vibration (often tied to blade or adapter wear)
- Deck rust-through or structural damage
Last updated: January 2026
What model number is the Craftsman 24738911?
The model number is 247.38911 (often written without the dot as 24738911) for this Craftsman walk-behind gas lawn mower. You can confirm it on the model label and in the parts diagrams listed in the 24738911 owner's manual.
On Craftsman walk-behind mowers, the model number is typically printed on a sticker or metal tag on the mower deck or rear housing.
- Check the rear of the deck near the discharge opening or rear skirt
- Look on the top of the deck near the engine mounting area
- Wipe off grass and dirt; the label can be hard to read when dirty
- Match the number exactly (including dots or dashes if shown)
You may see the same mower referenced as 247.38911 or 24738911. Both point to the same Craftsman model; the dot is a formatting style used on some labels and manuals.
| What you see | What it means | When it’s used |
|---|---|---|
| 247.38911 | Model number with dot formatting | Common on manuals and ID labels |
| 24738911 | Same model number without the dot | Common in parts lookup and ordering |
This mower can also have an engine model number and part numbers listed separately. For example, the manual shows an engine model number (used for engine-specific parts) that is different from the mower model number.
- Mower model number: 24738911
- Engine model number: used for engine parts only (carburetor, spark plug, air filter)
- Part numbers: identify individual replacement parts (blade adapter, wheels, grass bag)
Using the exact mower model number helps us match the correct parts diagrams and ensure items like the mulching blade, blade adapter, and grass catcher fit your specific deck and handle setup.
Last updated: January 2026
